I'm using an 18v makita hammer drill with a 3/16" Bosch blue granite turbo concrete bit to drill 2" deep holes into concrete-filled cinder blocks. With a fresh bit, it takes about 15 seconds to drill a hole. By the 4th hole, it slows to a crawl and it takes 2-3 minutes to drill a complete hole. After the 5th hole, the bit is completely shot and I have to get a new bit. I've gone through half a dozen bits now, trying to discover what I'm doing wrong - and I have no idea.
The hammering action of the drill isn't activating, so i'm losing all of the impact potential - I can't really apply any more force than I am already, as the drilling is happening over-head at an awkward angle... Any idea if there's a reason the bits dull so quickly? Is this a better job for an impact drill?
I should also say that I can't notice any visible difference on the tip of the bit - it doesn't look blunted, or marred, which is part of why it's so puzzling. I don't have a means to sharpen it, but just from visual inspection it looks OK